Method and device to use multiplied pressures for automatic altitude adjustments for aircraft



Nov. 4 1924. 1,513,870

S. W. SPARROW METHOD AND DEVICE TO USE MULTIPLIED PRESSURES FOR AUTOMATIC ALTITUDE ADJUSTMENTS FOR AIRCRAFT Filed July 25. 1923 2 Sheets$heet. 1

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gnuenhbz S. W. SPARROW METHOD AND DEVICE TO USE MULTIPLIED PRESSURES FOR AUTOMATIC ALTITUDE ADJUSTMENTS FOR AIRCRAFT Filed July 25 1923 2 Sheets-Sheet gjwuewroz adorn:

Patented Now. t, 119241.

' STANWOOD SPARROW, OF MIDDLEBORQ, MASSACHUSETTS.

METHOD AND DEVICE TO USE MULTIPLIED ,PRESSURES FOB. AUTOMATIC ALTITUDE ADJUSTMENTS FOR AIRCRAFT.

Application filed July 25, 1923. Serial No. 653,826.

(FILED UNDER THE ACT OF MARCHB, 1883, 22 STAT. L, 625.)

To all whom it may concern: of the aims of the method of altitude com- Be it known that I, S'rANwooD W. SPAR- pensation herein described. To this end the now, a citizen of the United, States and resimost important step is a change in the dent of 'Middleboro, county of Tlymouth, method of operating'the automatic device; State of Massachusetts, have invented a new The change suggested is to make the source and useful Method and Device to Use Multiof operation the diiference between atmosplied Pressures for Automatic Altitude Adpheric pressure and some multiple of atmosjustments for Aircraft, of which the followpheric pressure greater than 1 instead of I ing is a specification. the difference between atmospheric pressure 1 This invention may be used by the Govand that of a gas confined in a tight chamernment or by any of its officers or ember. Tabulated values of the differences beployees, or by any other person in the United tween atmospheric pressure and twice and States, in the prosecution of work for the ten times atmospheric pressure respectively Government without payment of any roymay be stated as follows: alt thereon. A

his invention is a method and apparatus 2-1 10-1 to use pressures Whlch are a constant mul- Apmximate altitude (feet). Bg gg gi 2333f; a i-1f, tiple of varying atmospheric pressures for (Om,Hg egg j g egg fg automatic altitude adjustments designed in'.).' iii. o more particularly for use on aircraft, al-

though it is obvious that it is applicable to g other uses. 7 52 10:1 91

The efiicient performance of an aircraft :3 g 7 requires that certain adjustments be made 25 as the ressure of the air through which the aircra 't passes becomes changed. Hence, Using 2 as the multiple gives a force for there is the altitude control of the can; operating the adjustment equal to that buretor which enables the pilot to maintain which would be obtained in the conventional so the desired air-fuel ratio. Recent develop device if the sealed chamber were completely so 'ments have increased both the number and evacuated. With the higher multiples suiimportance of such adjustments. For excient pressure'is obtained to make it unnecample, the safety of the over-dimensioned essary either to provide a relay or to make engine depends upon the careful manipulathe unit of large dimensions to care for adtion of spark advance and throttle opening justrnents whose operation requires considand aproper control of a variable pitch erable force. propeller is necessary it the maximum per- A practical device based on the herein deformance of a supercharged engine is to be scribed method of altitude compensation is obtained.

shown in the accompanying drawing, but it so Brier to this invention some schemes ,exis to be understood that the device there isted for automatic compensation.- Nearly shown is for the purpose of illustration only all of "these automatic controls are essenof one type of practical embodiment and not tially the same in principle. Their chief eleas defining the limits of the invention. ment is tight chamber containing a gas .In the drawingsas (usually When the atmospheric pres- Figure 1 is a vertical, sectional View sure changes the resultant change in the through a pump and its reservoir with its diderence between it and the pressure of the movable wall to effect changes in adjustgas with the chamber causes motion of meat;

some Wei the chamber. This motion ef- Figure 2 is a fragmentary view of the defects the desired ad ustment. vice of Figure 1, showing the plston and I in such devices a leak in the supposedly control valve in their lower positions;

v he iber means utter failure. The Fi'ure 3 is a similar view. disclosing soelinim or this source of danger is one called sylphon or metal bellows type of sion stroke,

where F -absolute pressure at beginning of compression stroke,

V =v0lume at beginning of compression stroke,

P =absolute pressure at end of compresn=exponent having a value between 1.3 and 1.4,

V =volume at end of compression stroke, V V and n are constant for any given pump and hence the quantity is also constant. This relation can be chosen to give any multiple of the initial pressure that is desired. Since, with adequate port opening, 1? is very nearly atmospheric pressure it is evident that the compression pressure of a pump of this sort is a constant multiple of the pressure of the air which surrounds it. This is the condition sought.

Referring more particularly to Figures 1 and 2 of the drawings, there is shown a base 1 having a piston chamber 2 within which is mounted a piston 3 having the usual connecting rod 4 connected to the piston by means of piston pin 36. Leading to the piston chamber 2 is shown a port 5 to permit air to enter the chamber 2. An end wall 6 may be provided with ports 7 leading from the chamber 2 to an intermediate chamber 8 formed by a wall 9. Mounted on this wall 9 by an suitable means is an element forming a ird-chamber 1O surrounded by the wall 11, which wall may have a depending section 12 to protrude into the intermediate chamber 8. Chambers 8 and 10 together constitute and function as a single reservoir, being made separately in this instance solely for convenience in construction. The third member may have a shoulder 13, shown in ing boss 17 designed to pass through an aperture 18, the urpose of which will be hereinafter descri ed.

Suitably secured to the wall 11 of the third member is an end wall 11 to form one end of the reservoir consisting of chambers 7 8 and 10. The end wall 11 may be provided with a central opening through which passes a control rod 19, shown secured at one end to a movable element, such as the wall 20, mounted within the chamber 10. 0

This. control rod 19 may be connected to adjust the carburetor control (not shown) or the spark advance device (not shown) or the propeller adjustments (not shown). If

desired, the movement of the wall 20may be resisted or limited in one direction by a resilient element, shown in the drawings as a spring 21, positioned between the movable wall 20 and the end wall 11. It is undermg to prevent leakage of the air or gas under compression.

. stood that in practice the piston 3, the mov- The reservoir section 11 may be provided also with a gauge 32 leading to the reservoir 10 to disclose the pressures within'the reservoir.

An alternative method of construction is shown in Figure 3. In lieu of the piston of Figure 1 a so-called sylphon S is used as a pumping means. In this construction air is admitted through poppet valve 24 closed. by a spring 25 except during that portion of the cycle when the valve stem base.1. In lieu of chamber 10 in Fi re 1 another sylphon T may be used. This sylphon is provided with a movable portion or wall 22 with which may be connected the control rod 19.

. When the piston is in its lowest position, as in Fig. 2, air or through port 5. On its upward stroke the piston 3 first closes this port and then comgas enters the cylinder abuts against presses the air above it in chamber 2. This process continues until the pressure in the reservoir is approximately the same asthat in the chamber 2 at the end of the compression stroke of the piston 3. From thenon, the piston 3' merely compresses and re-expands the same charge and its operation requires an amount of power only slightly in. excess. of that necessary to overcome the piston friction. If the valve 16 was constructed without the depending boss 17, the device would function satisfactorily only when the w reservoir chambers 8 opened control believed it will aircraft was descending; that is to say, when the compression pressure was increasing.

.With the compression pressure decreasing, as in passing from a lower to a higher altitude, check Valve 16 would fail to open and the pressure in'reservoir chambers 8 and-10 would cease to be a constant multiple of the pressure of the surrounding atmosphere. The remedy is to open positively a passage between the pump of piston chamber 2 and and 10 for a short time during each cycle. This permits an equalization of reservoir and cylinder pressures regardless of whether the atmospheric pressure is increasing or decreasing. To secure this positive opening check valve 16 is pro.- vided with the boss 17, previously referred to, which-comes in contact with the head 23 of the piston and causes the valve 16 to be lifted from. its seat for a short distance; for example, about nd of an inch at each revolution. When the pressure in reservoir chambers 8 and 10 changes, the wall 20 of Figure 1, or a similar element 2) of Fig. 2, moves until the pressure of the spring 21 on one side balances the difference in pressure between the air or gas inside the reservoir 10 and that outside of the reservoir. It is to be understood that the same principle applies to the embodiment shown in Figures 3 and 4 in addition to which the sylphon S has the poppet valve 24, which may be when its shank or boss engages the base 1. It is the movement of the elements 20 or 22 which causes a movement of the rod 19 attached to the desired instrumentalities of the aircraft equipment and which actually effects the desired adjustment. By 32, the pilot of the aircraft can determme,

whether or not the device is functioningproperly. The piston may, if desired, be driven direct from the aircraft engine or by any other suitable means.

It is obvious that it is possible to operate several devices of control mechanisms 0 the aircraft from a single pump installation. This would require merely that each individual reservoir should have a movable element such as a wall 20, and that each wall should be. connected by a pipe with the main reservoir 10. Such multiple control mechanism. is not herein illustrated as it is be readily understood by those skilled in the art.

Having thus described my invention, what I claim as new is 1. In a device of the class described, a

reservoir having a movable element, means to pump air into the reservoir to cause the pressure of the air in the reservoir to become a constant multiple of the surrounding atmospheric pressure, and a valve interpose between the pumping means and the reservoir, said valve having means adapted to sure within able element to balance the pressure between the air within the reservoir means of the pressure gauge and the surrounding atmospherlc air, means f the be opened positively for a portion of each cycle to permit an equalization of reservoir and pump pressure. I

2. In a device of the class described, a reservoir having a movable element, means the pump air into the reservoir to cause the pressure of the air within the reservoir to become a constant multiple of the surrounding atmospheric pressure, a valve interposed between the pumping means and reservoir and having means to maintain the valve in a closed position, said valve having a boss adapted to be engaged by the pumping means to lift the valve from its seat at the compression stroke of the pumping means to thereby equalize the pressure within the reservoir -with the pumping compression multiple of the pressure of the surrounding atmosphere, and means carried by said movable element to indicate. changes of pressure. 3. In a device of the class described, a reservoir having a movable element provided with a resilient member to cause said move able element to balance the differences in pressure between the air within the reservoir and the surrounding atmospheric air, means to pump air into the reservoir, a valve int rposed between the pumping means and the reservoir, and means whereby the pumping means or the pressure of the compressed gas may open the valve to equalize the resof atmospheric pressure pumping means.

4. In a device of the class described,-a reservoir having a movable element provided with a resilient element to cause said movditferences in produced by the to pump air into the reservoir, a valve intermeans may open the valve on the compression action of the pumping means to equalize ressure within the reservoir with the multiple of the pressure of the surrounding atmosphere produced by the pumping means, and means connecting the movable element of the reservoirwith an instrumentality to be affected. a

5. In a device of the class described, a casing within which is mounted an expansible reservoir having a plurality of rigid end Walls, one of which is movable as the reservoir expands, a check-valve in one of said .walls, a check-valve positioned intermediate the rigid walls and within the reservoir, means to admit air into the reservoir and release it therefrom to cause the-pressure o the air in'the reservoir to become a constant multiple of the surrounding atmospheric d pressure, and means to connect the movable end wall of the reservoir to an instrumentality to be actuated.

the reservoir with the mu tiple 6. The method of using multiplied pressures for altitude adjustments for aircraft which comprises the storage of air at nearly atmospheric pressure within .the reservoir having a movable wall to which adjusting devices are connected, thereafter introducing air into the reservoir or withdrawing air from the reservoir until the compression pressure of the air is a. constant multiple of the surrounding atmospheric pressure wherebythe movement of the movable wall due to the difference between the pressure within the reservoir and the surrounding atmospheric pressure will effect the desired adjustments of aircraft mechanisms.

7. The method of adjusting an element which controls the driving mechanism of aircraft'to' altitude which -c0mprises the storage of a gas within a reservoir at a pres sure which is a multiple of the atmospheric pressure where the storage is eflected, and thereafter introducing gas into the' reservoir or withdrawing gas therefrom in ac-, I

cordance with variations in atmospheric pressure as may be needed to make the pressure in the' reservoir the same multiple of atmospheric pressure.

8. The method of adjusting an element which controls the driving mechanism of aircraft toaltitude which comprises the storage of a gas within a reservoir which is in communication with a pressure indicator at a pressure which is a multiple of atm0spheric'pressure where the storage is effected, and thereafter introducing gas into the reservoir or withdrawing gas therefrom through control means which permits gas to enter the reservoir or escape therefrom in accordance with variations in atmospheric pressure as may be needed to make the pressure in the reservoir the same multiple of atmospheric pressure, until the indicator shows that such pressure in the reservoir has been attained.

STANWOOD W. SPARROW. 

